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MON Ibis. Darlene Reuss August 15, 1990 Page 2 Hydrocarbons as gasoline (TPH-G), ND to 12,000 ppm for TPH as diesel (TPH-D), and ND to 380,000 parts per billion (ppb) for Benzene, Toluene, Ethylbenzene, and total Xylenes(BTEX). The highest hydrocarbon concentrations were found in soil samples from borings B9, 1310, and fill from depths of 20 to 30 feet. Ground water was not found in any of the borings. Regional hydrologic information indicates that first ground water may be expected at a depth of approximately 75 feet. The predominant soil type found in the borings from approximately 5 to 50 feet was a fairly homogeneous, moderately loose silt to clayey silt. The objectives of this investigation are to determine if hy water. drocarbons have vertically migrated to the ground water and, if so, to assess the extent of hydrocarbons in the ground WORK PLAN To accomplish the above objectives, ESE presents the following work plan: 'ASK 1 Drill and Sample Two 4-inch Diameter Ground-Water Monitoring Wells. The proposed Iocatioms of the two ground-water monitoring wells(DTI and DT2) CLt, are shown on Figure 2. Based upon regional hydrologic information, wells � ¢-� DTI and DT2 should be approximately upgradient and downr respectively, of the soil containing hydrocarbons. The weIIs will be drilled with a hollow-stem auger to 10 feet below the first ground water found; total depth of the wells is expected to be approximately 85 feet. Soil samples will be obtained while drilling with a split-spoon sampler at 10- foot intervals and significant lithology changes. The samples will be logged and described by an ESE geologist. Hydrocarbons are not expected to be found in the soil, however the samples will be screened with an Organic l,Qr, Q L Vapor Analyzer (OVA). If soil samples have an OVA reading greater than ppr , the sample from the deepest part of the unsaturated zone, and the sample with the highest reading,will be sent to a laboratory to be analyzed for TPH-G, TPH-D, and BTEX. The wells will be screened with 4-inch diameter, 0.02 inch slotted polyvinyl chloride (PVC) pipe from total depth to approximately 10 feet above the saturated zone. Blank PVC pipe will extend to the surface. The wells will be sand-packed from total depth to 5 feet above the slotted section, I foot of bentonite pellets will be added and bentonite hole plug will be used to seal the annulus to 10 feet from the surface. Neat cement will seal the final 10 feet to a watertight traffic box at the surface. At least 24 hours after construction,water level measurements_will be made,--------- _..-,-the well elevations will be surveyed to a common datum, and the wells will --- - --- --- - -